This turns out to be a huge plus for “The Host,” the cinematic sci-fi romance that has been winnowed down from Meyer’s 625-page heavy-breather and ably fit into just over two hours of movie by writer-director Andrew Niccol. Niccol has been into the future before, with 1997’s “Gattaca” and 2011’s “In Time,” and he knows how to bring a modicum of smarts to a slab of deep purple.

The novel, of course, was Meyer’s follow-up to her “Twilight” series, and it has some of the same obsessions. Instead of a girl torn between a hunky vampire and a werewolf to die for, “The Host” is about a girl and a girlish alien sharing one body while torn between two cute human guys. This plot might lend itself to exploring themes of the divided emerging self, or the eternal conflict between Id and Super-ego, or — nahhh, it’s mostly about kissing boys.

Still, “The Host” is a marked improvement over the “Twilight” movies, especially the last few. (There’s no character with a name as headbangingly stupid as Renesmee, for one thing). In the near future, Earth has been conquered by the Souls, aliens that look like glowing woolly bear caterpillars and who slip into humans, take over their consciousnesses, and turn their eyes fluorescent. Melanie Stryder (Saoirse Ronan), one of the few free humans left, is captured early in the film and forcibly mind-melded with the Wanderer, an alien with a good heart and a rebellious streak.

It’s a little like the old Jeff Bridges movie “Starman” with the genders reversed, then serialized for Seventeen magazine. Melanie fights back against the invader in her own skull, so we get scenes of Ronan talking to herself, first in person and then in voice-over. The star (“Atonement,” “Hanna”) is maturing into a graceful older presence and she’s certainly talented enough to pull off the double act without looking too ridiculous. I’d hate to see Kristen Stewart try, though; the effort might kill the poor thing.

THE HOST

★★½

MPAA rating:

PG-13

MPAA rating reasons:

Some sensuality and violence

Running time:

121 minutes

Cast:

Saoirse Ronan, Max Irons, Jake Abel, William Hurt, Diane Kruger

Director:

Andrew Niccol

Writers:

Andrew Niccol (screenplay), Stephanie Meyer (novel)

Playing at:

Boston Common, Fenway, suburbs

The two — wait, one — escape confinement, gradually coming to a wary truce, and work their way to a desert cave complex peopled by a band of human survivors. They’re led by eccentric old Uncle Jeb (William Hurt!) and include among their number the more or less identically handsome Jared (Max Irons, Jeremy’s son) and Ian (Jake Abel). In the world according to Meyer, sincere young men with no body fat are apparently stacked up like cordwood.

Jared loves Melanie, while Ian loves the Wanderer, whom the group eventually warms to and rechristens Wanda. Complications arise. “It’s not really me you like, it’s this body,” the alien visitor tells Ian. She later complains to Melanie, “You’re angry when I kiss a man you do love and angry when I kiss a man you don’t.”

And you thought seventh grade was hard.

“The Host” is dramatic tapioca made surprisingly watchable by the performances — nothing brilliant but professional — by the dramatic mesas and buttes of New Mexico, by the director’s eye for arresting visuals and his ability to keep the story from grinding to a halt. Except for one extremely tetchy alien (Diane Kruger) bent on capturing Melanie/Wanderer, the invaded Earth doesn’t seem like such a bad place at all. No wars, everyone’s nice, the groceries are free. What’s the fuss?

The fuss is that these benevolent conquerors don’t know how to feel passion — real passion, womanly passion, Stephenie Meyer passion — and it’s up to one alienated adolescent alien to lead the way, aided by an overbearing musical score that does the swooning for everyone. “The Host” will make perfect sense to 12-year-old girls, while their college-age sisters will probably laugh themselves sick and their mothers will look at Hurt and wonder when he got so old. And, if nothing else, the movie serves as an excellent substitute for the book: better art direction and a quarter of the adjectives.